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Update VecDeque implementation to use head+len instead of head+tail (See #99805) This changes `alloc::collections::VecDeque`'s internal representation from using head and tail indices to using a head index and a length field. It has a few advantages over the current design: * It allows the buffer to be of length 0, which means the `VecDeque::new` new longer has to allocate and could be changed to a `const fn` * It allows the `VecDeque` to fill the buffer completely, unlike the old implementation, which always had to leave a free space * It removes the restriction for the size to be a power of two, allowing it to properly `shrink_to_fit`, unlike the old `VecDeque` * The above points also combine to allow the `Vec<T> -> VecDeque<T>` conversion to be very cheap and guaranteed O(1). I mention this in the `From<Vec<T>>` impl, but it's not a strong guarantee just yet, as that would likely need some form of API change proposal. All the tests seem to pass for the new `VecDeque`, with some slight adjustments. r? `@scottmcm` |
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| .. | ||
| arc.rs | ||
| autotraits.rs | ||
| borrow.rs | ||
| boxed.rs | ||
| btree_set_hash.rs | ||
| c_str.rs | ||
| const_fns.rs | ||
| cow_str.rs | ||
| fmt.rs | ||
| heap.rs | ||
| lib.rs | ||
| linked_list.rs | ||
| rc.rs | ||
| slice.rs | ||
| str.rs | ||
| string.rs | ||
| thin_box.rs | ||
| vec_deque.rs | ||
| vec.rs | ||